Breaking down the microbiology world one bite at a time
Waste Food into novel cuisine: courtesy Neurospora intermedia
Each year, millions of tonnes of food gets wasted while many people across the globe go hungry and are malnourished. It is disheartening to note that almost 33% of the food produced worldwide is either lost in supply chains or gets wasted, leading to tremendous greenhouse gas emissions. However, a recent collaborative study has demonstrated that food waste streams like rinds, peels, husks, and the left-overs from the food industry can be “upcycled” into novel healthy food sources that can be both delicious and nutritious using Neurospora intermedia fermentation.
The study explored a traditional fermented food known as Oncom, prepared by East Javanese farmers from Indonesia from oilseed by-products. A nutrient-dense source of protein that can be consumed without any form of processing, Oncom has been cherished for ages in Indonesian cooking. In recent years, scientists have isolated the fungus Neurospora intermedia as a major driver for Oncom fermentation.
How does Neurospora intermedia work?
Researchers collected 10 samples of red Oncom (produced from soymilk by-product Okara) and 6 samples of black Oncom (produced from peanut oil leftover press cake).
They employed cutting-edge techniques called shotgun metagenomic sequencing (the study of DNA from microbial samples) and transcriptomics (the study of gene activity) to understand particular characteristics of microbes present in Oncom. Here’s what they found out:
1. Neurospora intermedia is a Wasting-Eating fungus
N. intermedia was the main fungus (> 95%) of the red Oncom microbial population due to solid-state fermentation (SSF). By sequencing and comparing Neurospora intermedia’s genome with other fungi, it has been found that this strain possesses some distinctive genes responsible for the degradation of plant materials, making it particularly efficient in upcycling food waste. The biochemical tests revealed that enzymes in N. intermedia cleave and digest complex carbohydrates such as cellulose and pectin found in okara and other crop by-products. This results in simple sugars such as glucose and galactose, which are utilized by this fungus in its growth.
2. N. intermedia boosts the Nutritional Value and Palatability
Okara Oncom fermented with N. intermedia is enriched in amino acid content, most notably glutamine and glutamate, that impart the umami taste to Oncom. SSF also produces high levels of antioxidants, including ergothioneine, which is found in oyster mushrooms and has exhibited several functional benefits in humans.
3. N. intermedia is safe for consumption
Most fungi produce mycotoxins, which are harmful for human consumption. But based on secondary metabolite production, N. intermedia has not been known to produce any mycotoxins, even when grown on new materials, making it safe for food manufacture and consumption.
More Than Okara: A Fungus for All Food Wastes
In order to establish whether N. intermedia can be applied to other food by-products fermentation, scientists tested it on 30 different food waste types, including fruit and vegetable pomace, oil-seed press cakes, scraps, and by-products of plant-based milk, crop processing, and breweries. The fermentation outcomes assessed based on the growth of fungal mycelia and conidia were quite interesting and commendable. The fungus thrived on the majority of these food waste by-products and converted them to energy-rich biomass. While almond milk by-products, carrot peels, and pumpkin seeds were all great for the fermentation process, some raw materials, such as grape pomace and olive pomace, were not conducive to the growth of fungi. This study pinpointed the large scope of application of N. intermedia. on a wide variety of food waste streams to be upcycled into healthier food alternatives.
Though sustainability is a crucial factor for the circular economy, would people really want to consume food made from fermented waste? To ascertain this, scientists conducted a Check-All-That-Apply consumer survey on 61 Danish consumers who had never tasted Oncom before. The Danish participants tasted fermented pan-fried okara and showed positive responses. Many respondents characterized the taste as ‘nutty’, ‘earthy’, and ‘mushroom-like’ while giving high scores for flavor, texture, and appearance. The fascinating thing was that Oncom was enjoyed by a non-native population, making it clear that fermentation does wonders for food waste by increasing its sensory appeal.
a) More than 50% of consumers indicated the taste to be nutty, mushroom-like, and fermented.
b) The majority of consumers ranked high in liking the flavor, texture, and appearance. Adapted from Maini Rekdal V. et al.
In terms of logistics, as opposed to huge conventional fermentation tanks, which are capital intensive, the SSF with fungi like N. intermedia is a feasible, relatively uncomplicated, and cost-effective alternative. It can convert by-products into protein-rich foods with superior taste that are easier to cultivate than conventional animal proteins. This approach can be conveniently modified for use even in rural settings. Hence, SSF proved to be an appropriate technology for industrialized economies as well as resource-poor areas.
This study successfully demonstrated the waste-coping capability of N. intermedia fungus in converting food waste into appetizing and healthier foods, which can be a step closer to food security and sustainable food alternatives. This study was a unique take on drawing from cultural and indigenous wisdom to ensure a more sustainable and zero-waste future.
Written by Sushma Varma
Featured image: Representative image of Oncom Merah (Midori, Wikimedia Commons https://commons.wikimedia.org/wiki/File:Oncom_merah.JPG)
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